1. Field of the Invention
The present invention relates to a composition for coating and, more particularly, to a composition that can form a coating film having water resistance, acid resistance and non-flammability merely by applying it to the surface of metal such as aluminum, stainless steel and iron, or the surface of a base material such as concrete, ceramic, stone, cement manufacture, wood, paper, and fabric, or the surface of an inorganic coating film, and then performing air-drying or heating at low temperatures for a short period of time. This coating film can therefore contribute to the corrosion prevention of concrete buildings, the corrosion prevention of metals, and the prevention of spreading fire and smoke pollution during a fire.
2. Description of the Background Art
A variety of compositions for coating (hereinafter referred to simply as a “composition”), which are used for forming a coating film that combines water resistance, acid resistance and non-flammability on the surface of a base material, have traditionally been proposed, and various compositions using binder of alkali silicate are disclosed.
Specifically, it is known that alkali silicate such as sodium silicate, potassium silicate and lithium silicate can form a dry film or cured film by air-drying or heating at temperatures of 500 to 800° C. Although these are used as binder for forming a coating film having acid resistance and non-flammability, there is a problem that a film formed by drying alkali silicate at ordinary temperatures has poor water resistance. Therefore, in order to impart water resistance to a film formed by a composition using alkali silicate as binder, there has been proposed a method of using a composition in combination with acid or basic material as curing agent. In other words, alkali silicate exhibits alkality in strong acid solution, and hydrate of silicate in pure water acts as acid (see page 60, “Water Glass” written by Meyer. H., translated by Susumu Okuda, first edition, 1950, issued by CORONA PUBLISHING CO., LTD.). Hence, acid and basic materials have been useful as curing agent.
However, the use along with curing agent has the following problems. That is, a composition combined with curing agent will be solidified, and hence it has poor long-term shelf life. This involves such operational complications that curing agent must be incorporated in a composition for each coating operation.
Here, it is known that a composition in combination with curing agent has the property of setting to gel for a short period of time and loosing fluidity; and that the speed at which the composition sets to gel is affected by the type of curing agent and the amount of addition and temperature conditions of curing agent. Therefore, when coating a composition combined with curing agent, the gelation of the composition will interfere with coating operation. Consequently, there arises such complications in handling that, to retard the speed at which the composition sets to gel, it is necessary to make adjustment such as the determination of the type of curing agent or the modification of the amount of addition of curing agent.